This invention relates rubber compositions and tire components, especially tire treads, where the tire components and compositions include a metal hydroxide filler and a modified polyolefin additive.
Rubber compositions, especially those used to prepare tire components, have traditionally been filled with carbon black. The need for tires that have less rolling resistance and improved wet traction led to the use of other fillers such as silica.
While silica filled tires provide reduced rolling resistance, especially when used in conjunction with a silane coupling agent, silica filled tires suffer from other disadvantages. For example, silica filled tire treads have a lower storage modulus than carbon black filled tire components. Also, the use of coupling agents, such as silane coupling agents, is expensive because overall raw materials costs increase and processing techniques must be adapted to compensate for the use of the silane.
Aluminum hydroxide has also been employed to achieve improved rolling resistance. As with silica, however, the use of aluminum hydroxide as a filler in combination with carbon black, silica, or both, improves rolling resistance at the sacrifice of other properties such as mechanical strength and toughness.
Because tire components that derive from rubber compositions including metal hydroxides, such as aluminum hydroxide, as a filler show some advantages, there is a need to offset the disadvantages associated with the use of these metal hydroxide fillers.
In general the present invention provides a tire component formed by a process comprising the steps of (A) vulcanizing a rubber composition comprising (1) a rubber, (2) a modified polyolefin additive, (3) an aluminum hydroxide filler, and (4) a rubber vulcanizing agent.
The present invention also includes a tire component prepared by a process comprising the steps of (1) mixing a rubber with from about 0.1 to about 25 parts by weight per 100 parts by weight rubber of a modified polyolefin additive, from about 1 to about 25 parts by weight per 100 parts by weight rubber of an aluminum hydroxide filler, and a vulcanizing amount of vulcanizing agent to form a tire compound, and (2) subjecting the tire compound to curing conditions.
The present invention further includes a tire component comprising (1) a rubber, (2) from about 0.1 to about 25 parts by weight per 100 parts by weight rubber of a maleic anhydride modified polypropylene, and (3) from about 1 to about 25 parts by weight per 100 parts by weight rubber of a metal hydroxide filler.
The use of polyolefin additives within tire compositions that include metal hydroxide filler, such as aluminum hydroxide filler, has advantageously offset many of the problems that have been associated with the use of metal hydroxide filler. In fact, the use of the polyolefin additive described herein has surprisingly lead to the discovery that both rolling resistance and handling performance can simultaneously be improved. Additionally, the combination of metal hydroxide and polyolefin additives within tire tread compositions has lead to the discovery that heat aged mechanical properties of the treads are stabilized despite the presence of the plastic.